Conventionally, combustion heaters that heat a radiating body with combustion heat generated by combustion of fuel gas and heat an industrial material or food with radiant heat from a radiating surface of the radiating body have been widely used. In such combustion heaters, for example, to increase radiant intensity, a technology of applying a high-emissivity material or shape to the radiating surface has been proposed (e.g., see Patent Document 1).
Further, a combustion heater known as a micro combustor for improving heat efficiency has been proposed. This combustion heater increases heat efficiency by forming a range from an inflow passage of fuel gas to a combustion chamber and an outflow passage of exhaust gas after combustion in a sealed structure, making the inflow and outflow passages adjacent to each other, and preheating the fuel gas prior to combustion with heat of the exhaust gas (e.g., see Patent Document 2).